The present invention relates to a signal processing apparatus and method, a recording medium and a program, and more particularly to those adapted for minimizing the required processing to realize more adequate insertion of packets each indicative of discontinuity of a stream or the like.
There is currently observed wide diffusion of digital television broadcasting which compresses television program data composed of video and audio data on the basis of high-efficiency encoding technology conforming with the MPEG (Moving Picture Experts Group)-2 system or the like, and broadcasts the compressed program data via a satellite.
A viewer can select a desired program by manipulating an STB (Set Top Box) which is a terminal to receive and reproduce the digital television broadcast waves, and displaying an EPG (Electronic Program Guide) and so forth.
In the MPEG-2 mentioned above, there is provided a multiprogram function for transmitting a plurality of programs inclusive of program data, wherein the respective programs are time-division multiplexed in the form of transport packets which are relatively short units of transmission.
A plurality of transport packets constitute a transport stream, which is processed by the STB.
FIG. 1 is a diagram for explaining a transport stream to be processed by the STB.
The stream shown in the upper row is termed a full stream wherein the program to be reproduced has not yet been selected by the viewer. The full stream consists of packets (1st, 5th, 8th) representing the data of a channel (program) A, packets (2nd, 7th, 10th, 11th) representing the data of a channel B, and packets (3rd, 6th, 9th, 12th) representing the data of a channel C.
An SI (service information) packet (4th) is included in the full stream of FIG. 1. There is described, in this packet, service information to indicate which packet is to be extracted and decoded for reproducing the program.
The stream shown in the lower row in FIG. 1 is termed a partial stream extracted from the full stream in response to a command sent from the viewer for reproduction and so forth. The example of FIG. 1 denotes one case where the viewer has selected the channel A.
As shown in the partial stream of FIG. 1, the 1st, 5th and 8th packets representing the data of channel A are extracted, and the service information described in the 4th packet is rewritten, so that a new SI packet is included as a 23rd packet.
More specifically, out of the entire service information in the full stream, only the descriptor relative to channel A selected by the viewer is described in the SI packet (23rd), whereby the SI packet (4th) used in the broadcast is no longer included in the partial stream.
When the service information has been rewritten after extraction of the partial stream from the full stream, there occurs discontinuity of the stream and the service information (change in the switching or the description contents). Therefore, as shown in FIG. 1, packets (21st, 22nd) each having a stored discontinuity information table (DIT) indicative of a discontinuity point are inserted in the discontinuity points.
The discontinuity information table indicates a discontinuity point of a stream or the like as mentioned, and any fault that may be caused by reproduction of the stream discontinuity point is avoided on the basis of such information. For example, in case the stream to be reproduced is a video stream, the information is used for eliminating reproduction of the discontinuity point, or for blacking out the reproduced stream to thereby realize no display of the corresponding video image.
However, in any conventional STB known heretofore, there exists a problem that, when a packet containing a described discontinuity information table is inserted, the information needs to be entirely re-described each time, hence increasing the processing load to a great extent.